1. Field of the Invention
The present invention relates generally to third-generation mobile networks, and specifically to media gateways within third-generation mobile networks.
2. Description of Related Art
Third-generation mobile networks are described in the 3G TS 23.002 (3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Network architecture, Release 5) (hereinafter referred to as the Technical Specification). As described in the Technical Specification, third-generation mobile networks logically divide the infrastructure into a Core Network and an Access Network.
The basic Core Network is constituted of circuit-switched nodes, such as Mobile Switching Centers (MSCs), packet-switched nodes, such as General Packet Radio Service support nodes (SGSNs) and control nodes, such as Home Location Registers (HLRs). The basic Access Network is constituted of radio control nodes and radio access nodes. As an example, the radio control nodes may be Base Station Controllers (BSCs) for GSM (Global System for Mobile Communications) radio networks and Radio Network Controller (RNCs) for UMTS (Universal Mobile Telecommunications System) radio networks. As a further example, the radio access nodes may be Base Transceiver Stations (BTSs) for GSM radio networks and Node Bs for UMTS radio networks.
Third-generation mobile networks also partly utilize a layered network architecture. Call control and connectivity, which have traditionally been bundled in telecommunications networks, are now separate layers within the Core Network circuit-switched domain. This separation is achieved by dividing the MSCs into media gateways and network servers. The call control layer is resident in the MSC servers, while the connectivity layer is resident in the Media Gateways.
The Media Gateways serve to bridge the different transmission technologies and to add service to end-user connections. The Media Gateways use open interfaces to connect between the Core Network and an Access network. The media gateway control interface (H.248) facilitates this separation of call control and connectivity layers. Media Gateways are located within the Core Network as an interface to both the Access Networks and to legacy networks, such as the Public Switched Telephone Network (PSTN).
Recent advances in third generation mobile networks have made it possible to have each Media Gateway controlled by a single network server or multiple network servers. For example, as described in an article by Fryo et al. entitled “Media gateway for mobile networks,” which was published in Ericsson Review No. 4 on Nov. 30, 2000, and which is hereby incorporated by reference, a single Media Gateway may be controlled by more than one network server within the Core Network by the use of Virtual Media Gateways within the Media Gateway. Each Virtual Media Gateway is controlled by one network server, with resources being shared by all of the Virtual Media Gateways.
However, by implementing the Media Gateways within the Core Network, call control and connectivity are not separated in the Access Network. Therefore, Media Gateways cannot be shared between the Access Network and the Core Network. In addition, for calls between Access Networks served by the same MSC server, physical transmission of payloads (e.g., speech or data) between the Access Networks and the Core Network is still required.